Sometimes the printer may run out of filament in the middle of a print. The printer does not have any way to know that it’s run out of filament. If at all possible, it’s best to catch this right away so that the printer doesn’t continue to stay hot without filament moving through it, as this can burn the filament onto the nozzle—ABS is particularly prone to this.
If your print runs out of filament and can’t reverse material to remove the piece, there is an alternate way to get it out.
For Ultimaker 2 series machines: go to Maintenance —> Advanced —> Heat Nozzle on the menu and raise the temperature to 230. The number on the left is the nozzle’s actual temperature; the number on the right is the temperature you’ve set it to.
For Ultimaker 3 series machines: go to Material/Print Core --> Print Core 1 (or 2) --> Set Temperature on the menu, and raise the temperature to 230. The number on the left is the nozzle’s actual temperature; the number on the right is the temperature you’ve set it to.
When the printer has finished heating, slide the horse-shoe shaped clip out of of the printhead. For Ultimaker 2 series machines, this clip will be blue; for Ultimaker 3 series this clip is white. Push down on the white collet, and pull the bowden tube up.
There should be some amount of material sticking out of the tube, which you can grip and pull out.
Following this, reseat the bowden tube in the printhead, making sure that it sits inside the Teflon coupler, as demonstrated in the picture below. Continuing to push down on the bowden tube, raise the white collet and slide the blue clip firmly in place beneath it.
Below is a picture of the correct seating for an Ultimaker 2, Ultimaker 2 Extended, or Ultimaker 2Go printhead.
For an Ultimaker 2+ or Ultimaker 2 Extended+ printhead, you can check the seating by looking above the collet and making sure the indentations from the collet aren't visible; when the bowden tube is seated all the way, they should be hidden by the collet. On all Ultimaker 2 series printers, the collet marks are about 2 inches from the end of the tube.
For an Ultimaker 3 or Ultimaker 3 Extended, the bowden tube should be seated as far down as it will go; it's only a few millimeters. In the picture below, you can see how close the collet marks are to the end of the bowden tube.
If your printer ran out of filament during a long print where the printer was not monitored (such as an overnight print) and the nozzle remained hot for a long period of time, without filament moving through it, you may need to conduct a cleaning using the Atomic Method after removing the filament, to take care of any burnt on obstructions.